Results from a genetic test, can you tell me what it means?

Question

My 8 week old nephew has been through a series of genetic tests and the doctor just told us that on the p22.31 X chromosome there is a duplication on the arm. I have searched and searched and am unable to find anything specicifc that results from this abnormality. The doctor has yet to tell us exactly what to expect from this, if you have any info at all I would be happy to hear it, good or bad. Thank you in advace!

Answer 1

If you have the nomenclature correct, this sounds like a duplication syndrome of the X chromosome.  The 'p' is indicating that the duplication is found on the "short arm" of the chromosome (there are two arms, called 'p' and 'q', which are connected by something called a centromere).  The p22.31 refers to the location or 'locus' on that chromosome.

There is not going to be a whole lot of information about this specific anomaly because it is quite rare.  It is not a famous syndrome like Down, so probably the reason the doctor is not giving you a whole lot of information is that s/he doesn't really have a whole lot to draw from.  With these unusual anomalies, it's difficult to tell what the outcome will be because there are numerous genes on any chromosome and what may result depends on exactly how many of them are duplicated and what they do.  I don't have the genetic report, so the information you are giving me is limited.

I am going to give you a couple of links, but please--please!--understand that genetics is a very complicated subject and it is well-nigh impossible to predict the actual course that any given patient will have.  I would strongly encourage your brother or sister (the parent) to contact a genetic specialist.

http://bjp.rcpsych.org/cgi/content/full/...  This is a case report of a family with two children with a similar genetic abnormality.

http://www.ncbi.nlm.nih.gov/Omim/getmap....  This is the OMIM (Online Mendelian Inheritance In Man) page with a general overview of the genes that are at that locus.

Please note that none of this information is indicative of what your nephew may or may not have.  There is no way to tell, so please don't click on all the potential disorders and worry yourself into the ground that he will have any or all of them.  This is just so you have some information that you can look over and perhaps formulate questions to ask the doctor, if you are involved with your nephew's care.

Answer 2

Genetic duplications or deletions can be bad, or, if people are lucky, they can be "silent". They are usually not a good thing. Boys have only one X chromosome, thus they are prone to problems if their only X chromosome has abnormalities. Genetic analysis is in its infancy and we have only identified the tip of the ice burg. In some cases, we have found that many genes  need to be affected to produce a noticeable problem in a person; however, in other cases, only one duplication/deletion will dramatically affect a person. In your nephews case, the duplication is in the small arm of the X chromosome (it runs in families and the abnormality can be given to the son from the mother). This abnormality has been seen in some people with learning disabilities. But it's hard to say, since learning disabilities may be an interaction of multiple genes and not just this one. Why did he have a genetic analysis done?